With advantages such as high luminous efficiency, energy saving and long service life, light emitting diode, or LED, has been widely applied. For daily lighting, an LED lamp usually integrates a plurality of power LEDs in order to meet the illumination requirement, and heat dissipation of the LEDs turns out to be an important factor affecting use status and service life of an LED lamp. Consequently, the cooling problem becomes a technological bottleneck impeding extensive application of high-power LED lamps. LED lamps in the prior art are passively cooled down by devices like heat dissipation plates of a heat sink, and the only way to improve the cooling efficiency is to maximize the cooling area. Accordingly, LED lamps in the prior art generally have a large size because of a complicated cooling structure, and yet the cooling efficiency is unsatisfactory. The applicant of the present invention has developed an LED lamp with combined active and passive heat dissipation by integrating a cooling fan with a heat sink, which exhibits excellent cooling efficiency with effectively improved stability and extended service life. However, lamps of very high power such as high bay lights require even better cooling efficiency and therefore usually adopt an open type structure that results in poor waterproof and dustproof effect, impeding their application under outdoor and special environment.
In addition, a thermal silicone grease with a thermal conductivity of 3 W/(m·K)-4 W/(m·K) and a thermal insulating cloth with a thermal conductivity of 2 W(m·K)-3 W/(m·K) are currently used between a light source board and a heat sink for insulation and thermal conduction, both having a rather low thermal conductivity and thus exhibiting rather poor conductive efficiency. A thermal silicone grease is a fluid paste hard to apply evenly, and this will not only lower its thermal conductivity, but also impair the insulation performance between the light source board and the heat sink, or even cause a short circuit between the two. A thermal insulting cloth is also hard to apply evenly as it may be easily deformed, and is not efficient to use as it is hard to place it between the light source board and the heat sink.